dbcve.org
FirefoxWeb browser · Mozilla

CVE-2025-1012

HIGH · 7.5 CVSS v3.1 Published 2025-02-04
Fix available
A fix is available. Upgrade to 115.20.0 / 128.7.0 or later.
See remediation →
82/100
Remediation priority · High
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A race during concurrent delazification could have led to a use-after-free. This vulnerability was fixed in Firefox 135, Firefox ESR 115.20, Firefox ESR 128.7, Thunderbird 128.7, and Thunderbird 135.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A race condition during concurrent delazification in Firefox and Thunderbird could lead to a use-after-free vulnerability, allowing potential memory corruption and possibly arbitrary code execution.

MitigationUpdate to Firefox 135, Firefox ESR 115.20, Firefox ESR 128.7, Thunderbird 128.7, Thunderbird 135 or later versions. Deploy through standard patch management processes.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FirefoxWeb browser
Affected:< 115.20.0< 135.0>= 128.1.0, < 128.7.0
ThunderbirdApplication
Affected:< 135.0>= 128.0.1, < 128.7.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check if Firefox is installed and its version
    Run 'firefox --version' on command line, or on Windows check the version in 'C:\Program Files\Mozilla Firefox\firefox.exe' properties, or on Linux check via package manager (dpkg -l firefox or rpm -qi firefox)
    Affected if Firefox version is less than 115.20.0, OR between 128.1.0 and 128.6.x inclusive, OR less than 135.0 (excluding 115.20.0-115.x and 128.7.0+)
  2. Check if Thunderbird is installed and its version
    Run 'thunderbird --version' on command line, or on Windows check the version in 'C:\Program Files\Mozilla Thunderbird\thunderbird.exe' properties, or on Linux check via package manager (dpkg -l thunderbird or rpm -qi thunderbird)
    Affected if Thunderbird version is between 128.0.1 and 128.6.x inclusive, OR less than 135.0 (excluding 128.7.0+)
  3. Identify all Firefox ESR deployments
    Check for ESR (Extended Support Release) installations via package manager or by running 'firefox --version' - ESR versions include 115.x and 128.x branches
    Affected if Firefox ESR version is less than 115.20.0 OR between 128.1.0 and 128.6.x inclusive
  4. Check for concurrent browser usage patterns
    The vulnerability triggers during concurrent delazification (lazy parsing of JavaScript). Users who have multiple tabs or windows open simultaneously and browse JavaScript-heavy websites are more likely to trigger the race condition
    Affected if Multiple tabs or windows are used concurrently with JavaScript-heavy web content - the race condition occurs during normal browsing when multiple such operations overlap

A user is affected if they have Firefox version < 115.20.0, < 135.0 but >= 128.1.0, or < 128.7.0 on the 128.x ESR branch; or Thunderbird version < 135.0 but >= 128.0.1, or < 128.7.0 on the 128.x ESR branch - particularly when using multiple tabs or windows with JavaScript content concurrently.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 115.20.0 / 128.7.0 / 135.0 or later
Fixed in 115.20.0128.7.0135.0
Interim mitigation

Update to Firefox 135, Firefox ESR 115.20, Firefox ESR 128.7, Thunderbird 128.7, Thunderbird 135 or later versions. Deploy through standard patch management processes.

Recommended fix High confidence

Firefox 135 / Firefox ESR 115.20 / Firefox ESR 128.7 / Thunderbird 135 / Thunderbird 128.7 (depending on current channel)

  1. Identify the currently installed Firefox or Thunderbird version via Help > About (or running 'firefox --version' or 'thunderbird --version' in terminal)
  2. If using Firefox Stable: Upgrade to Firefox 135 or later
  3. If using Firefox ESR 115.x: Upgrade to Firefox ESR 115.20 or later
  4. If using Firefox ESR 128.x: Upgrade to Firefox ESR 128.7 or later
  5. If using Thunderbird Stable: Upgrade to Thunderbird 135 or later
  6. If using Thunderbird ESR 128.x: Upgrade to Thunderbird 128.7 or later
  7. Restart the application after upgrade and verify the version via Help > About
Caveat Most users will not experience breaking changes; however, verify that critical add-ons are compatible with the target version before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2025-1012 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-1012 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data